Stabilization of lubricating oils with a ketene



STABILIZATION OF LUBRICATING OILS WITH A KETENE James L. Jezl, Swarthmore, Habet M. Khelghatian,

Springfield, and Archibald P. Stuart, Media, Pa., assignors to Sun Oil Company, Philadelphia, Pa, a corporation of New Jersey No Drawing. Filed Nov. 25, 1959, Ser. No. 855,252

4 Claims. (Cl. 208-291) This invention relates to the stabilization of lubricating oil, and more particularly to treating lubricating oil with an agent capable of reacting with unstable constituents of the lubricating oil.

Lubricating oils from petroleum or other sources, e.g. shale, frequently have unsatisfactory color and oxidation stability as a result of the presence of unstable constituents in small amounts in the lubricating oil. The nature of the unstable constituents is not definitely known, and appears to differ for various petroleum fractions of different molecular weight and type of crude base. In some instances, the unstable constituents appear to be nitrogen compounds. However, in other instances, the effect of nitrogen compounds does not. appear to be particularly important, and the lack of stability seems to be attributable to certain high molecular weight hydrocarbon constituents of the oil.

In view of the differences between various petroleum fractions, the stabilizing of the various fractions presents different problems depending upon the nature of the fraction. The present invention provides a treating process which is remarkably eflective in stabilizing the heavier fractions of petroleum, and particularly lubricating oil fractions derived from paratfinic-naphthenic, or intermediate, base petroleum crudes. The process is also beneficial however as applied to lubricating oils derived from other types of crude base or from shale, etc. Motor oils, transformer oils, refrigerator oils, spindle oils, etc. are examples of lubricating oil products to which the invention is beneficially applied.

The lubricating oils which are treated according tothe invention have Saybolt Universal viscosity at 100 F. of at least 50 seconds, and more preferably at least 100 seconds. The treatment is applicable to lubricating oil distillate fractions and also to distillation residues which contain lubricating oil components. The charge oil is in any event free of the lower boiling fractions occurring in crude petroleum. Less than 20% of the charge stock according to the invention boils at atmospheric pressure at a temperature below 700 F., and in some embodiments less than 5% of the constituents boil below 700 F. Usually the Saybolt Universal viscosity of the charge stock at 210 F. will not exceed 300 seconds, although higher viscosity charge stocks can be treated if desired.

The charge stocks treated according to the invention generally do not contain any significant amount of mercaptans, and are higher boiling and more viscous materials than those which are customarily subjected to sweetening operations. The charge may contain 0.01% or less of nitrogen compounds, though the invention is also applicable to charges containing more nitrogen.

The process according to the invention involves contacting hydrocarbon lubricating oil with a ketene, i.e., a compound having the formula RR"C=C=O where R and R are alkyl, aryl or hydrogen groups. A preferred ketene for use according to .the invention is ketene itself wherein R and R are both hydrogen. Ketenes constitute a known class of compounds, as disclosed for example in R. L. Kirk et al. Encyclopedia of Chemical Technology," pages 109-113 (1952) and the references cited therein. Examples of suitable ketenes for use according to the invention are ketene, methyl ketene, ethyl ketene, dimethyl ketene, diethyl ketene, diphenyl ketene, etc. The ketene may be generated for example in the manner disclosed in E. Arundale et a1. Patent No. 2,608,520, August 6, 1952.

Suitable temperatures for the treatment according to the invention includes those above 30 F. Highly satisfactory stabilization can be accomplished in many cases by treatment at roomtemperature or below. In some instances the use of elevated temperature may be advantageous in order to accelerate the sabilizing operation, but temperatures above 180 F. are generally unnecessary and are typically avoided in order that polymerization of ketene and other competing reactions should not occur to an excessive extent.

If desired the treatment can be performed in the presence of an acidic catalyst, e.g. mineral acid, acid-activated clay, etc.

The process according to the invention is particularly advantageous as applied to lubricating oils obtained from intermediate base crude having viscosity-gravity constant (I. B. Hill and H. B. Coats, Industrial and Engineering Chemistry, volume 20, page 641, 1928) within the ap proximate range from 0.83 to 0.88. Naphthenic base lubricating oils having viscosity-gravity constant greater than 0.88, and parafiinic base lubricating oils having viscosity-gravity constant less than 0.83 can also be beneficially treated according to the invention however. Preferably the charge stock according to the invention has A.P.I. gravity within the approximate range from 20 to 28.

The following examples illustrate the invention:

Example I The charge stock was a dewaxed blend of a furfuralrefined distillate and a'duosol-refine'd residue from mixed base (paraflinic -naphthenic base) crude, the crude hav ing viscosity-gravity constant of about 0.84. Typically such blends have initial boiling point of about 650 F., 5% point of about 740 F. and point of about 1020 F. The blend was stirred at 32 F., and 1.5% ketene based on blend was passed in over a 30 minute period. After standing overnight, the blend was distilled to remove first a fraction constituting 1% of the charge and then recover a lubricating oil distillate constituting 73% of the charge, leaving a 26% residue. Typically, such a 1% fraction has Saybolt Universal viscosity of about 40 and has a distillation endpoint of about 660 F. Typically, such a lubricating oil distillate has nitrogen content of only about 0.005% and contains about 23% based on charge of a fraction having Saybolt Universal viscosity at F. of about 100 seconds and boiling range of about 660 to 820 F., and contains about 50% based on charge of higher boiling and more viscous components; typically, it has an endpoint between 950 and 1000 F.

The lubricating oil distillate was washed with water. The following table shows the NRA. color, interfacial tension in dynes per centimeter, and acidv number in mg. of KOH per gram, of the washed distillate, after aging for 96 hours at 280 F. in the presence of 0.4% of 2,6- ditertiary butyl-p-cresol, as compared with a control distillate obtained in a generally similar manner but without ketene treatment, the distillation being performed in the presence of clay for decolorization.

This example shows that a remarkable improvement in color stability can be obtained by treatment of paraffinic-naphthenic base lubricating oil with ketene according to the invention, and the stability of'the oil is also greatly improved with respect to resistance to formation of acidic materials and lowering of interfacial tension upon aging.

Example 11 The charge stock was a straight run distillate from naphthenic base crude, the distillate typically having initial boiling point at atmospheric pressure of about 560 F., 20% point of about 730 F., 50% point of about 780 F., endpoint (99%) of about 885 F., and Saybolt Universal viscosity at 100 F. of about 700 seconds. The treatment with ketene was essentially similar to that described in Example I. The treated oil was tested for oxidation stability by placing a 0.1 gram sample in a flask filled with oxygen and determining the time elapsed before the pressure in the flask decreased by 20 mm. of Hg while maintaining the sample at 280 F. A relatively long life in this test indicates good resistance of the oil to taking up oxygen. Tests were made with 0.1% of 2,6-ditertiary butyl-p-cresol as oxidation inhibitor, and also in the absence of oxidation inhibitor. The following table shows'the results in these tests, comparing the ketene treated oil with the same oil not treated with ketene.

Life in Hours 7 Inhibited Uninhibited Ketene-treated lube 011...- Untreated lube oil Generally similar results are obtained in treatment of parafi'inic base lubricating oils or lubricating oils derived from shale in a manner generally similar to that described in Examples 1 and II. Generally similar results are also obtained employing other ketenes such as those mentioned previously.

' In the above described treatment of naphthenic base lubricating oil, the color stability of the uninhibited, ketene-treated lubricating oil was poorer than that of the uninhibited untreated lubricating oil, indicating that in the case ofnaphthenic base lubricating oil the treatment according to the invention is primarily beneficial with respect to resistance to other effects of oxidation than color degradation.

The reaction products of ketene with constituents of the charge stock are preferably separated from the treated oil in the process according to the invention, although in some instances an improvement in the oil is obtained without such separation. A preferred manner of, eifecting such separation is by distilling the treated oil from the less volatile reaction products, though any other suitable method can be employed, such as selective adsorption or selective solution in polar'solvents of the reaction products, etc. Preferably the distillate 'oil is water washed, such washing frequently being effective to remove odorous materials of unknown composition from the distillate.

This application is a continuation-in-part of application Serial No. 679,137, filed August 20, 1957,'now

abandoned.

The invention claimed is:

1. Process for improving stability of hydrocarbon lubricating 'oil which comprises: contacting hydrocarbon lubricating oil having 20% point at atmospheric pressure of at least 700 F., with a ketene, thereby to react said ketene with unstable constituents of said oil.

2. Process according to claim 1 wherein said oil is a paraflinicrnaphthenic base oil.

3. Process according to claim 1 wherein the treated lubricating oil is separated from the ketene reaction products by distillation.

4. Process according to claim 1 wherein said oil comprises residual material.

References Cited in the file of this patent UNITED STATES PATENTS 

1. PROCESS FOR IMPROVING STABILITY OF HYDROCARBON LUBRICATING OIL WHICH COMPRISES: CONTACTING HYDROCARBON LUBRICATING OIL HAVING 20% POINT AT ATMOSPHERIC PRESSURE OF AT LEAST 700* F., WITH A KETENE, THEREBY TO REACT SAID KETENE WITH UNSTABLE CONSTITUENTS OF SAID OIL. 